AIUI Dewalt was primarily a woodworking tool firm (or it grew from a woodworking tool firm). I guess their designs were focussed on that material and their customers were mainly working with wood. That is a simplification, but perhaps there's something in it.
Nonetheless the carpenter/joiner tradesman we know uses Makita which he considers better for joinery. Makita tools I've seen in shops are the more expensive of the brands.
Bosch was always an engineering firm across multiple sectors, and is a wealthy corporation with huge resources for product development, so I'd expect their stuff to 'just work'.
In an age of battery power tools, each brand produce systems of tools that share a common proprietary battery, and so consumers will stick with one brand. (A strategy of non-compatibility with other brands is also used by DSLR camera manufacturers and bike component manufacturers.)
I have no brand loyalty.